Network with most members. They offer free accommodation and travel help. Includes a forum, chat and travel guides. Available in many languages. http://www.hospitalityclub.org
Online community based on the concept of offering a couch to visitors. To become a verified member, payment by credit card is required. http://www.couchsurfing.com
Nonprofit cultural exchange organization promoting friendship and goodwill through an extensive program of homestay exchanges since 1977. http://www.friendshipforce.org
For women only. Aims to foster international friendship by enabling women of different countries to visit one another. There is a membership fee. http://www.womenwelcomewomen.org.uk